This is a Shannon Award providing partial support for research projects that fall short of the assigned institute's funding range but are in the margin of excellence. The Shannon award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. As preterm infants are frequently unable to breastfeed, mothers desiring to supply them with breastmilk must develop their milk supply through manual or mechanical milk expression techniques. Unfortunately, many experience problems with diminishing milk volume over time and the preterm infant fails to receive the many benefits of human milk. Higher milk yields and higher prolactin levels have been found in mothers of twins who breastfeed the two infants simultaneously. The purpose of this longitudinal study is to compare the effects of sequential single vs. simultaneous double breast pumping on milk volume in mothers of preterm infants who must mechanically pump for an extended period to time. In addition, this study will examine the impact of stress, prolactin, oxytocin and pumping regimen on milk volume. The research questions are: (1) What are the differences (weeks 2,3,4,5,6) in milk volume based on pumping regimen? (2) What is the impact of stress and pumping regimen on the volume of milk? (3) What is the impact of stress, prolactin, oxytocin and pumping regimen on the volume of milk? (4) What are the best predictors of lactation status at 12 weeks? The sample will consist of 128 mothers of preterm infants who will be randomly assigned to either a single or double pumping system. Four measures of stress will be used on days 7, 14, 21, 28, 35, and 42: salivary amylase and cortisol for measures of physiologic stress and a Visual Analogue Scale and the Multiple Affect Adjective Check List-Revised for measures of psychologic stress. For a subsample of 50 subjects who agree to venipuncture, the total amount of oxytocin and prolactin secreted in association with the breast pumping procedure will be analyzed. These data will be important to identify the best technique to maintain lactation in mothers of preterm infants in order to provide the infant with the benefit of human milk and the nursing experience. In addition, these data will further an understanding of the potential influence of stress, oxytocin, and prolactin on milk yield in mothers of preterm infants.